Khairullozhon Matanov, a taxi driver who is in his early 20s and living in Quincy, Mass., is accused of lying to investigators about how well he knew Tamerlan Tsarnaev – the relationship involved shared extremist beliefs, US officials say – and misleading officials about the extent of his contact with the Tsarnaev brothers in the days after the bombings.

Mr. Matanov, who has been in the United States since 2010, is charged with one count of destroying, altering, and falsifying records and three counts of making false statements in a federal terrorism investigation, according to the indictment. He was arrested Friday morning and is scheduled to appear in court in the afternoon.

Federal prosecutors allege that Matanov “participated in a variety of activities with Tamerlan Tsarnaev, including discussing religious topics and hiking up a New Hampshire mountain in order to train like, and praise, the ‘mujahideen,’ " according to the indictment.

On the evening of April 15, 2013, after two bombs had splintered through a crowd at the Boston Marathon that afternoon, Matanov allegedly spent more than 40 minutes on the phone with the older Tsarnaev brother and then invited both of them to dinner, buying their meals, prosecutors say. According to the indictment Matanov, who allegedly expressed support for the bombings after hearing about them, visited the older brother at his home in Cambridge, Mass., on April 17.

That's pretty detailed already. The current accusation is that he only knew about the bombings after the fact. Then we have some of the Muslim friends who saw bomb materials. All that suggests is that they may have had accomplices after and before the fact.